The 18x10" ET25 supports the 275/35/18 tire sidewall very well, any larger and the tires will balloon a bit. We would recommend sticking to the 275/35/18 tire size for the best steering response and sidewall support.

I use a 18x10 et25 set up all around. With 3+ camber up front and 2+ in the rear.

Due to the amount of camber, I can easily use 10 mm spacers front and rear on 275/35/18 Continental scrubs. However, it is pretty tight in the rear (tire to fender) with spacers. There's plenty of room if you don't use spacers in the back.

Front space I cannot say since I have aftermarket struts.

One consideration is that there are not too many tires available in 285/35/18. 285/30/18 offers more but you would lose your side wall.

Another consideration is the balance. The M3 understeers from the factory, so depending on your set up you may prefer a square over a staggered.

The 18x10" ET25 supports the 275/35/18 tire sidewall very well, any larger and the tires will balloon a bit. We would recommend sticking to the 275/35/18 tire size for the best steering response and sidewall support.

Running the ARC-8s as noted above with Nitto NT01s and happy so far. No spacers.

I put a set of 275/35-18 Nitto NT-01's on a 9.5/10.5 wheel setup this evening. They are bulgy on the 9.5 and pretty square on the 10.5. They fit like 285's and would be perfect on 10's.

A 275 might sound small for a 10" wide wheel if it was a street tire, but the NT-01 runs really wide. You will have tons of room to the inside with this 275 on the 10 ET25 wheel, and it will completely fill it out.